BillFitzmaurice.info

rotebass wrote:
Standard rig for my consists of SRX728,

I've been sitting in with a band who has 4 of those and have used them on other sound gigs. They are great boxes - but the power requirements and weight make them back-breakers in two different ways.

You'll enjoy the efficiency and weight of the Tubas.....but don't expect a Tuba with 450 watts to blow away a 728 getting 2000 watts. But, it should hold it's own quite well with a single 18 getting 1000 watts. Build a herd of 'em and your back and your amp budget will thank you.

rotebass wrote:What I can do is try to document some of the pitfalls I encountered to try to help future novice builders save some time (2 hours sanding the driver cut out to correct size, going to have to rethink that step next time around lol).

That's a very worth while thing to do IMO!!

I built 3 baffles before I was happy!

I was sloppy to begin with and then really nailed the one that I built into the cab (T18).... only to change the driver after it was built. But then had to get into changing the holes because the new driver was a little different. What a nightmare that was. I almost gave up!

Lots learned there, I tell you!! I have a couple of threads going if you are interested...

Bruce Weldy wrote:

rotebass wrote:
Standard rig for my consists of SRX728,

I've been sitting in with a band who has 4 of those and have used them on other sound gigs. They are great boxes - but the power requirements and weight make them back-breakers in two different ways.

You'll enjoy the efficiency and weight of the Tubas.....but don't expect a Tuba with 450 watts to blow away a 728 getting 2000 watts. But, it should hold it's own quite well with a single 18 getting 1000 watts. Build a herd of 'em and your back and your amp budget will thank you.

Very power hungry, bridged MT2400 per cab and they still want more. Versus an XTI4000 to run 4 T30 (or 8 if you are willing to go to 2ohm per channel).

Late night update:

Got to the theatre (wood shop is in the basement) intending to make some serious progress, as soon as I got my sled clamped up to start sawing out the buggered panel my TD comes in and asks if I will clock in for a few hours to help him with some odd jobs. Two hours later we had chased a conduit from one end of the building to the other, got side tracked in the basement looking at old renovation photos, quoted out a pile of shiny new gear and had a run in with the theatre's "ghost" (or HVAC system as my rational brain likes to think).

Back to the shop, I cut out the offending piece of wood, using a hand saw and hammer/chisel to finish the job, resulting in this:
https://dl.dropbox.com/u/25226419/Photo ... 1%20PM.jpg

Very careful trimmed a new panel to size, affixed it in place with a brad nailed, lots of clamps and even more PL:
https://dl.dropbox.com/u/25226419/Photo ... 9%20AM.jpg
https://dl.dropbox.com/u/25226419/Photo ... 6%20AM.jpg

The plus side to putting my work off for a few hours, is the TD gave me a quick crash course on the router. After a lot of head scratching and measuring, I was able to produce my very first router jig
https://dl.dropbox.com/u/25226419/Photo ... 6%20AM.jpg

The corners aren't perfect, so I'm going to spend some time with some sandpaper cleaning it up, but I feel my first go with a router was acceptable.

Any thoughts, ideas or concerns at this point?

Put a few long-ish screws into that piece if you can. PL is strong, but butt joints are weak. I'd be a little paranoid of that piece maybe coming out with people tugging on it. Even just 2-3 screws driven from the front (and countersunk well to prevent splitting) to secure it well to the back and maybe two from the side would ease my mind.

rotebass wrote:Any thoughts, ideas or concerns at this point?

Don't piss off your neighbors. I couldn't help it, when I finished my most recent BFM sub I just couldn't resist.

Charles Warwick wrote:Put a few long-ish screws into that piece if you can. PL is strong, but butt joints are weak. I'd be a little paranoid of that piece maybe coming out with people tugging on it. Even just 2-3 screws driven from the front (and countersunk well to prevent splitting) to secure it well to the back and maybe two from the side would ease my mind.

I tried really hard to angle the cut, but there was no way to plunge the saw while it was set at 45'. I used a ton of PL and a good quantity of brad nails, you don't think that would be enough?

Charles Warwick wrote:Don't piss off your neighbors. I couldn't help it, when I finished my most recent BFM sub I just couldn't resist.

Neighbour to one side of me is a car guy, I don't complain about his Charger starting up at 7:00am and he doesn't complain about the sounds coming out of my basement, it's a good arrangement. The neighbour to the other side is at work most of the time, although apparently I've rattled pictures on their walls with just the studio monitors hooked up to my Mac

rotebass wrote:
Very careful trimmed a new panel to size, affixed it in place with a brad nailed, lots of clamps and even more PL:
Any thoughts, ideas or concerns at this point?

You'll have no problems there, the joint with the inserted piece will be stronger than the plywood.

rotebass wrote: The plus side to putting my work off for a few hours, is the TD gave me a quick crash course on the router. After a lot of head scratching and measuring, I was able to produce my very first router jig
https://dl.dropbox.com/u/25226419/Photo ... 6%20AM.jpg

The corners aren't perfect, so I'm going to spend some time with some sandpaper cleaning it up, but I feel my first go with a router was acceptable.

Any thoughts, ideas or concerns at this point?

One thing I learned about jigs is they don't have to be nice. For a square or rectangular hole in a jig, it's very easy to cut straight "outside" cuts as opposed to the inside cuts of a jig like that. Cut 4 pieces of wood with straight edges, 2 of them longer, then pl them together to make your jig (don't worry about the square corners).

OR, and this is my favorite, drill out a hole in the 4 corners of the jig (i don't always do this), use a fence on a bandsaw, and just cut through the edge on one side, do your inside cut all the way around, and remove from the bandsaw on your first cut. Insert a sliver of scrap to prevent the jig from closing (if you like, I usually don't), and you're done. Doesn't have to be nice, it'll be clamped so it won't move. Also, the hole in the cab doesn't have to be perfect because the handle will cover the edge, but if your jig is straight, the hole in the cab will be straight as well, IF you're inserting a handle.

Got the project back on track and made some good progress tonight. Decided to have a second go making the handle jig, which was well worth the effort in my opinion because it resulted in this:
https://dl.dropbox.com/u/25226419/Photo ... 2%20PM.jpg
https://dl.dropbox.com/u/25226419/Photo ... 5%20PM.jpg

Then sanded down the edges
https://dl.dropbox.com/u/25226419/Photo ... 1%20PM.jpg

Did some more sanding and then rolled on the first coat of paint:
https://dl.dropbox.com/u/25226419/Photo ... 8%20AM.jpg
https://dl.dropbox.com/u/25226419/Photo ... 0%20AM.jpg

Really happy with the progress so far. I know it doesn't measure up to some of the work on this site, but it is quite satisfying to be on the home stretch of my first real project.

P.S. I realize this is turning into a build thread, if mods think it is more appropriate feel free to move it where it belongs.

Good for you!

You made a great recovery and should indeed be proud of your efforts!

Yes, perhaps your build is not quite as tidy as some (bet it's tidier than some others though lol), but you got a good result and learned some things in the process. Your next build will be easier as a result.

Congratulations...

Been swamped with contracts the last few weeks (2 week theatre run at one venue almost every night, number of other jobs at other venues during the day), finally got a chance to do some preliminary testing on my T30 last night. The testing was very much subjective, the opponent was a JBL SRX718S, mid-high for music listening was provided by a bi-amped SRX715. Amplification was provided by an XTI4000.

At this point I'm not sure how I feel, both cabs seem to have their strengths and weaknesses. The Tuba seemed to hold ground from 40-60 Hz (I ran a test tone at 35Hz as well, but didn't feel comfortable driving it up to 50V), above 60 Hz the 718S actually seemed to pull ahead by a noticeable margin (3-4dB), I was really expecting the T30 to pull ahead up higher, with the 718S taking the lead below due to the smaller mouth of a single Tuba. One thing I did notice, was that at 80-90Hz, by the time you had applied about 40V, the Tuba was audibly being pushed too hard. I wish I could record the sound it was making, but it sounded similar to what I've heard some BR cabs sound like shortly before biting the dust. Would this be evidence of an air leak? I was quite thorough in searching for leaks prior to sealing the driver chamber, I could pull it apart and have a third check, if it is an air leak then last nights testing was all in vain.

I plan to do some more work tonight, plan on moving my dB meter further from the cabs tonight (last night measurements were done at 1 M), I'm hoping this will take harmonic distorsion out of the picture. As a long time BR user, you don't realize how much distorsion is there until you hear a horn subwoofer.

rotebass wrote:above 60 Hz the 718S actually seemed to pull ahead by a noticeable margin (3-4dB)

Probably harmonics, an RTA would tell the tale.

I plan to do some more work tonight, plan on moving my dB meter further from the cabs tonight (last night measurements were done at 1 M)

You need to be at least 4m away, preferably 10m.

rotebass wrote:Would this be evidence of an air leak?

Probably.

Horns don't give any warning before they blow. They just stop making sound altogether when they do.